The most common types of congenital heart diseases include heart valve defects, heart muscle abnormalities and defects of the walls between the chambers of the heart, according to WebMD. The disease may be discovered shortly after birth or may not produce symptoms until adulthood.
Heart valve defects include valves that don't close properly, which leads to blood leaking backwards, WebMD explains. Valves can also be narrowed, creating decreased or blocked forward blood flow.
Defects of the walls between the chambers of the heart include holes or passages that can mix oxygenated and unoxygenated blood from either side of the heart, WebMD states. Heart muscle deformities can lead to heart attacks.
Most causes of congenital heart defects are unknown, WebMD maintains. Some risk factors do increase a child's likelihood of defects, including genetic or chromosomal abnormalities such as Down syndrome. Other risk factors include the mother contracting rubella during the first trimester of pregnancy. Mothers who take certain medications or abuse drugs and alcohol may also put their child at risk for congenital heart defects.
Congenital heart disease develops before a baby is born, WebMD says. Approximately 1 in every 100 children is born with congenital heart defects. About 500,000 adult Americans have congenital heart disease.